A process for brominating a styrenic polymer in an organic solvent in the presence
of an antimony trihalide catalyst such that a reaction mass containing brominated
styrenic polymer in an organic phase is formed is improved by mixing hydrochloric
acid or hydrobromic acid, or both, with said reaction mass at least once to extract
antimony catalyst residues from said reaction mass as an acidic aqueous phase.
Preferably, catalyst residues are recovered from the acidic aqueous phase and still
more preferably, recovered antimony trihalide catalyst residues are recycled to
constitute at least a portion of the antimony trihalide catalyst used in preparing
the brominated styrenic polymer.